If the sensor goes pink, then don't drink

Unlike wine, beer doesn't age well. It goes stale, becoming a foul-tasting concoction that breweries certainly shouldn't be sending out to stores or bars. While brewers do already perform tests to gauge freshness, those typically involve expensive gas chromatography equipment and take time to conduct. Soon, however, a simple color-changing sensor and an Android app may be all that's required.

Developed at Spain's Complutense University of Madrid, the technology incorporates small polymer discs that contain a derivative of the organic compound aniline. That derivative reacts with another compound that's given off by beer in increasing amounts as it ages, known as furfural – the greater the amount of furfural that's present, the more the disc will change in color from yellow to pink.

Users first expose one of the discs to a beer sample, and then take a photo of that disc on their smartphone. The app will analyze its color, determining a freshness rating based upon it. If the polymer has turned too pink, the beer will be deemed stale and undrinkable.

In lab tests performed on beers of varying ages, the new technology closely matched the accuracy of tests performed using more complex gas chromatography and mass spectrometry equipment.